Electric vehicle batteries are a lot like people, in one important respect: They’re most comfortable in temperatures around 65 to 75 degrees Fahrenheit.

When the weather gets much colder or hotter than that, a battery works less efficiently. It has to work harder, too, to keep the vehicle’s cabin comfortable for its equally picky human occupants.

The result? Electric vehicles can’t drive as far or as efficiently in extremely hot or cold weather.

AAA has been testing exactly how big an effect temperatures have on modern EV batteries. In its latest research, shared exclusively with NPR, it found that hot temperatures reduced range by an average of 8.5%. Cold weather cut vehicles’ range by a whopping 39%.